1. Field of the Invention
The present invention relates to a method for storing a brush used in a scrubbing process, and a container for storing such brush. The scrubbing process is performed, during the manufacturing process of an electronic device, to wash, make smooth, or impart a particular property to the surface of the semiconductor wafer or other substrate like a glass plate, on which the electronic device with a precise pattern is formed.
2. Description of the Related Art
In the manufacturing of a semiconductor device a dielectric film made of SiO.sub.2 or Si.sub.3 N.sub.4, or a conductive film made of, for example, TiN or polysilicon, is deposited on the surface of, for example, a semiconductor wafer. A chemical vapor deposition device or a sputtering device is used for the film deposition. When a film is being deposited by either of these devices, however, a film is also deposited onto an inner wall or an inner mechanism of a reaction chamber of the chemical vapor deposition device or of a vacuum chamber of the sputtering device. As the film gets thicker, it peels off as fine particles into the space in the reaction chamber or the vacuum chamber, and either sticks onto the surface of the desired thin film on the wafer, or is embedded into the thin film growing on the wafer, whereby a protrusion is formed, thus deteriorating the characteristics of a semiconductor device formed on the wafer and making the semiconductor device less reliable. Accordingly, the fine particles on the surface of a wafer or substrate are scrubbed away by a brush. In the manufacturing of a liquid crystal display (LCD) panel, the inner surface of a glass substrate is scrubbed using a brush in order to impart a property for aligning the orientation of the liquid crystal molecules to the surface.
The brush used for scrubbing the surface of a wafer or substrate formed of a fibrous or sponge-like member is attached to the surface of a disk-shaped member or a cylindrical surface of a drum-shaped member. The fibrous or sponge-like member is made of, for example, synthetic high polymers, such as polyvinyl alcohol, nylon, rayon, or polypropylene. The material is selected depending on the scrubbing to be performed, taking into account the hardness, flexibility, chemical resistance, and water resistance required. The present inventor has disclosed various brush structures (see for example Japanese Patent Application No. 05-220341).
In general, brushes formed by high polymer materials such as those mentioned above are washed after use, dried, and stored until they are used again. However, when brushes formed, in particular, of polyvinyl alcohol or rayon, and kept dry, are left exposed in the air, for example, for a few months, they change their physical and chemical nature. In other words, even when these types of brushes are made wet again, they often do not return back to their original form, recover their original resiliency, etc. Therefore, in the scrubbing process, the surface of the brush contacting to the semiconductor wafer becomes uniform, resulting in a non-uniform contact pressure therewith, so that the brush is no longer capable of scrubbing the wafer properly. In addition, brushes that have undergone physical or chemical changes cause wearing off when contacting to the wafer surface, thus making it easier for fine particles to be produced. In the scrubbing process, the fine particles stick onto the semiconductor wafer surface, so that these particles become a source of contamination.
Further, recent pattern dimensions in semiconductor integrated circuits, in terms of the gate length of a transistor for example, are in the order of a tenth of a micrometer, which is approximately equal to or less than the size of microorganisms such as bacteria. Therefore, exposing brushes, kept in a wet state, to the atmosphere causes microorganisms to multiply in the brushes. Consequently, such microorganisms are now being considered as contaminants of semiconductor wafer surfaces.